2587 Background: Dysregulation of HMTs plays an important role in tumorigenesis. KMT2C and KMT2D are enzymatically active scaffold proteins that form the core of mammalian COMPASS complexes, which methylate the histone 3 lysine 4. Both KMT2C and KMT2D are involved in the regulation of gene expression. Therefore, we explored the associations of KMT2C/D loss-of-function (LOF) mutations with the expression of immune-related genes, the levels of tumor infiltrating lymphocytes (TILs), and response to immune checkpoint inhibitors (ICIs). Methods: KMT2C/D LOF mutations were defined as nonsense, frameshift, splice site variants within consensus regions, start lost, and stop lost/gained variants. An ICIs treatment cohort from the MSKCC was used for exploring the associations between KMT2C/D LOF mutations and ICIs efficacy. The RNA-Seq data obtained from the TCGA cohort was used for analysis of gene expression and the levels of TILs using CIBERSORT. Results: In MSKCC pan-cancer dataset, patients with KMT2C/D LOF mutations had a relatively longer median overall survival (OS) compared to those with non-LOF mutations, although the result did not reach statistical significance (P = 0.0832). Then we analyzed the predictive roles of KMT2C/D LOF mutations for each cancer type. The results showed that the predictive role of KMT2C/D LOF mutations for the clinical efficacy of ICIs therapy was only observed in colorectal cancer (P = 0.045). However, we did not find the associations of KMT2C/D LOF mutations with ICIs efficacy in bladder cancer, breast cancer, melanoma, glioma, head and neck cancer, renal cell carcinoma, NSCLC, and esophagogastric cancer. Consistently, analysis of TILs in colorectal cancer revealed that KMT2C/D LOF was associated with increased infiltration of several types of immune cells, such as CD8+ T cells (P = 0.0001), activated NK cells (P = 0.0001), M1 macrophage (P = 0.0005), M2 macrophage (P = 0.0115), and neutrophils (P = 0.0209). Meanwhile, regulatory T cells (Tregs) (P = 0.0048) and M0 macrophage (P = 0.0043) were dramatically decreased in KMT2C/D LOF group for colorectal cancer. Moreover, there were no significant relationships between KMT2C/D LOF and the levels of TILs in other cancer types. Our data also demonstrated that KMT2C and KMT2D could regulate the expression of more than 30 immune-related genes in colorectal cancer. Conclusions: Our data indicated that KMT2C/D LOF mutations were significantly correlated with better outcomes of ICIs therapy in colorectal cancer, suggesting it can be as a useful predictor for response to ICIs in colorectal cancer. Meanwhile, we found the associations of KMT2C/D LOF with the levels of TILs in colorectal cancer, but not in other cancer types, indicating that the efficacy of ICIs was consistent with the levels of TILs.
Prediction of Benefit from Checkpoint Inhibitors in Mismatch Repair Deficient Metastatic Colorectal Cancer: Role of Tumor Infiltrating Lymphocytes